This invention relates to a device for refrigerating and/or freezing products with a treatment zone equipped with refrigeration equipment and a conveyor belt situated in the treatment zone for conveying the products through the treatment zone, the conveyor belt being supported by a supporting frame and guided over sliding rails mounted on the supporting frame.
Equipment in which the products are conveyed through a treatment zone in which refrigeration equipment is provided is often used for refrigerating and/or freezing products, in particular foods. For example so-called tunnel freezers in which foods are conveyed through a tunnel-like housing while a refrigerant, in particular a liquid gas such as liquid nitrogen, is sprayed onto the foods are in widespread use. For conveying foods through the tunnel freezer, a conveyor belt on which the foods are moved continuously through the tunnel freezer and are refrigerated and/or frozen in the process is generally used. Such conveyor belts typically have a width of 200 mm to 2000 mm, for example. The conveyor belts are supported mechanically from beneath as they are guided through the tunnel freezer due to the inherent weight and that of the product on the conveyor belt. A supporting frame of pipes, beams and plates is used for support. To minimize friction between the conveyor belt and the supporting frame, sliding rails, e.g., made of plastic, are mounted on the supporting frame, the conveyor belt being guided over these rails. The upper surface of the sliding rails is usually flat so that the conveyor belt is guided over them flatly. During freezing, product frequently adheres to the conveyor belt and it is difficult to release the frozen product from the conveyor belt at the end of freezing or this may be accomplished only with damage.
The object of the present invention is therefore to design a refrigeration and conveying device that prevents sticking of the products to the conveyor belt in freezing or at least allows frozen product that has stuck to the conveyor belt to be released without damage.
This object is achieved according to this invention by designing the sliding rails so they have a convex and/or concave shape on the top side in at least some sections, so that the conveyor belt slides on predefined curvatures.
This invention is based on the finding that it is very difficult to detach products from the conveyor belt at the end of the tunnel after freezing is complete. When product is released at the end of the tunnel, it not only results in destruction of the product but also damage to the conveyor belt. It is therefore proposed that the products be released from the conveyor belt already at a point in time when the connection between the product and the conveyor belt is not yet too strong. The product is therefore released from the conveyor belt not only at the end of the freezer but already within the freezer before the product has completely frozen and stuck. Therefore, the shape of the sliding rails is not flat on the top side but instead is convex and/or concave in at least some sections. The conveyor belt therefore does not slide flatly through the freezer but instead moves on specifically predetermined curvatures, i.e., radii, in at least some sections, so that a relative movement between the conveyor belt and the product creates shearing forces in the contact surfaces of the conveyor belt and product leading to detachment of the product.
The detachment of the products from the conveyor belt may also be accomplished repeatedly within the treatment zone. To this end, multiple convex and/or concave sections of the sliding rails are provided within the treatment zone. The shape of the elevation in the sliding rails may be designed differently. The sliding rails may also have a depression instead of an elevation, so the products become detached from the conveyor belt in a valley. A combination of elevation and depression of the sliding rails is also conceivable.
According to a particularly preferred embodiment of this invention, concave and convex sections of the sliding rails alternate along the direction of conveyance. This largely prevents products from adhering to the conveyor belt as they freeze.
This invention may be used with all conceivable devices for refrigerating and/or freezing products in which the products are conveyed through a treatment zone equipped with refrigeration equipment by means of a conveyor belt. This invention manifests its advantages most especially when used in tunnel freezers for freezing foods. In such tunnel freezers, spray nozzles for spraying liquid gas onto the foods are provided in the treatment zone.
A number of advantages are associated with this invention:
The products do not adhere so greatly to the conveyor belt in freezing because they are released in advance. Furthermore the products show little or no damage after the freezing operation. Product loss (rejects) is much lower. Since the products are released from the conveyor belt even before leaving the treatment zone, strippers mounted at the end of the freezer suffer less damage and therefore have much longer lifetimes.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.